1. Field of the Invention
The present invention generally relates to a system for administering focused energy to a body selectively using either a single energy applicator or multiple microwave applicators in order to treat visable tumors and microscopic malignant and benign cells in prostate tissue with hyperthermia. The system according to the invention may be used to treat healthy tissue containing undetected microscopic pathologically altered cells (neoplasia) that are of high-water content to prevent the occurrence of or the recurrence of cancerous, pre-cancerous or benign prostatic lesions. In addition, the disclosed system and method for using the system can prevent the growth of tumors inside the prostate, as well as prevent the spread of cancer cells outside the prostate.
2. Description of the Prior Art
In order to treat prostate tumors with hyperthermia, it is necessary to heat a significant portion of the prostate gland while sparing healthy tissues in the prostate as well as the surrounding tissues including the urethral and rectal walls of a patient. In the United States there are approximately 200,000 cases of detected prostate cancer annually as well as 375,000 cases of benign prostatic hyperplasia, known as BPH, (enlarged prostate gland). BPH is a non-cancerous enlargement (tumor) of the prostate gland that occurs in almost all men as they age, particularly past the age of 50 years. In the case of BPH, the enlargement of the prostate involves the excessive growth of tissue that eventually obstructs the bladder outlet, creating difficulties with urination. In the case of prostate cancer, eventually the cancer will break through the prostate gland capsule leading to the spread of cancer to the bones and vital organs of the body. Although some of the signs of BPH and prostate cancer are the same, having BPH does not increase the chances of getting prostate cancer. Nevertheless, a patient who has BPH may have undetected prostate cancer at the same time or may develop prostate cancer in the future.
As is known in the art, the use of heat to treat prostate tumors can be effective in a number of ways; however, in most cases, the heat treatment must be capable of heating a significant volume of the prostate gland without overheating the urethral and rectal walls. In radiation therapy, the entire prostate and adjacent tissues are irradiated with x-rays to kill all the microscopic cancer cells. While heating large volumes of the prostate can destroy many or all of the microscopic carcinoma cells in the prostate, known methods of heating tumors can destroy healthy tissue in the prostate and, more damaging, in the urethral and rectal walls of a patient.
The prostate gland has electrical properties similar to muscle (T. S. England and N. A. Sharples, Nature, Vol. 163, Mar. 26, 1949, pp. 487-488.) and is known to have a high-water content, on the order of 80% (F. A. Duck, Physical Properties of Tissue, A Comprehensive Reference Book, Academic Press, New York, p. 321, 1990). Tumor tissue, in general, tends to be 10 to 20% higher in water content than normal tissue (Foster and Schepps, Journal of Microwave Power, vol. 16, number 2, pp. 107-119, 1991). Thus, prostate tumors may have a water content on the order of about 90%. Accordingly, selective microwave heating of the prostate would be the best method of targeting cancerous or benign cells.
It is well known that microwave energy can heat high-water content tumor tissues faster when compared to the heating that occurs in lower-water content normal tissues. Tumor tissue tends to be poorly perfused so blood flow often decreases at therapeutic temperatures allowing rapid heating, while in normal tissues the blood flow often increases protecting the normal healthy tissue from heat damage. Many clinical studies have established that hyperthermia (elevated temperature) induced by electromagnetic energy absorption in the microwave band, significantly enhances the effect of radiation therapy in the treatment of malignant tumors in the human body (Valdagni, et al., International Journal of Radiation Oncology Biology Physics, Vol. 28, pp. 163-169, 1993; Overgaard et al., International Journal of Hyperthermia, Vol. 12, No. 1, pp. 3-20, 1996; Vernon et al., International Journal of Radiation Oncology Biology Physics, Vol. 35, pp. 731-744, 1996). Radio-resistant cells such as S-phase cells can be killed directly by elevated temperature (Hall, Radiobiology for the Radiologist, 4th Edition, JB Lippincott Company, Philadelphia, pp. 262-263, 1994; Perez and Brady, Principles and Practice of Radiation Oncology, Second Edition, JB Lippincott Company, Philadelphia, pp. 396-397, 1994). Hyperthermia treatments with microwave radiating devices are usually administered in several treatment sessions, in which the malignant tumor is heated to about 43xc2x0 C. for about 60 minutes. It is known that the amount of time to kill tumor cells decreases by a factor of two for each degree increase in temperature above about 43xc2x0 C. (Sapareto, et al., International Journal of Radiation Oncology Biology Physics, Vol. 10, pp. 787-800, 1984). Thus, a 60-minute heat-alone treatment at 43xc2x0 C. can be reduced to only about 15 minutes at 45xc2x0 C., which is often referred to as an equivalent dose (t43xc2x0 C. equivalent minutes).
During treatments with noninvasive microwave applicators, it has proven difficult to heat semi-deep tumors adequately while preventing surrounding superficial healthy tissues from incurring pain or damage due to undesired hot spots. The specific absorption rate (SAR) in tissue is a common parameter used to characterize the heating of tissue. The SAR is proportional to the rise in temperature over a given time interval times the specific heat of the tissue, and for microwave energy the SAR is also proportional to the electric field squared times the tissue electrical conductivity. The units of absolute SAR are watts per kilogram.
The first published report describing a non-adaptive phased array for deep tissue hyperthermia was a theoretical study (von Hippel, et al., Massachusetts Institute of Technology, Laboratory for Insulation Research, Technical Report 13, AD-769 843, pp. 16-19, 1973). U.S. Pat. No. 3,895,639 to Rodler describes two-channel and four-channel non-adaptive phased array hyperthermia circuits. Likewise, a non-adaptive phased array hyperthermia system was disclosed in U.S. Pat. No. 4,589,423 to Turner.
Bassen et al., Radio Science, Vol. 12, No. 6(5), November-December 1977, pp. 15-25, shows that an electric-field probe can be used to measure the electric-field pattern in tissue, and in particular, shows several examples in which the measured electric-field has a focal peak in the central tissue. This paper also discusses a concept for real-time measurements of the electric field in living specimens. However, Bassen et al. did not develop the concept of measuring an electric field using real-time with an electric-probe to adaptively focus a phased array.
The most difficult aspect of implementing hyperthermia in deep prostatic tissues, with microwave energy, is producing sufficient heating at a predetermined depth while protecting the urethral and rectal walls and surrounding organs from burns. Noninvasive multiple applicator adaptive microwave phased arrays with invasive and noninvasive electric field probes can be used for producing an adaptively focused beam at the tumor position with adaptive nulls formed in healthy tissues as described in U.S. Pat Nos. 5,251,645, 5,441,532, 5,540,737, and 5,810,888 to Fenn, all of which are incorporated herein by reference. Ideally, a focused microwave radiation beam is concentrated at the tumor with minimal energy delivered to surrounding healthy tissue. To control the microwave power during treatment, a temperature-sensing feedback probe (Samaras et al., Proceedings of the 2nd International Symposium, Essen, Germany, Jun. 2-4, 1977, Urban and Schwarzenberg, Baltimore, 1978, pp. 131-133) is inserted into the tumor, however, it is often difficult to accurately place the probe in the tumor. An additional difficulty occurs in delivering hyperthermia to carcinoma spread throughout the prostate gland, because of a lack of a well-defined target position for the temperature-sensing feedback probe. In other situations, it is desirable simply to avoid inserting probes (either temperature or E-field) into the prostate tissue in order to reduce the risk of infection or spreading the cancer cells when the probe passes through the tumor region.
Several articles have been written on the use of dual intracavitary (transurethral and transrectal) coherent phased array microwave applicators for prostate cancer treatment (A. Surowiec, et al., Hyperthermic Oncology 1992, Vol. 1, Summary Papers, Proceedings of the 6th International Congress on Hyperthermic Oncology, Apr. 27-May 1, 1992 (Arizona Board of Regents), p. 268 (abstract); M. M. Yeh, et. al. Hyperthermic Oncology 1992, Vol. 1, Summary Papers, Proceedings of the 6th International Congress on Hyperthermic Oncology, Apr. 27-May 1, 1992 (Arizona Board of Regents), p. 269 (abstract); and J. C. Camart, Hyperthermic Oncology 1996, Vol. 2, Proceedings of the 7th International Congress on Hyperthermic Oncology, Rome, Italy, Apr. 9-13, 1996, pp. 598-600). Further, U.S. Pat. No. 5,007,437 to Sterzer describes the use of non-coherent transurethral and transrectal applicators for BPH treatments. However, the known prior art is directed to the use of transurethral and transrectal applicators for treating solid tumor masses. None of the known procedures are concerned with treating microscopic disease and preventing the occurrence of solid tumor masses such that occur in cancer and BPH.
Prostate Cancer
The current standard of medical care for treating prostate cancer includes radical or nerve-sparing prostatectomy in which the entire prostate gland is surgically removed, and brachytherapy in which radiation seeds at low dose are permanently implanted in the prostate gland radiating effectively for 6 to 9 months or radiation seeds at high dose are temporarily implanted in the prostate for about 2 days, combined with external-beam radiation therapy to catch microscopic cancer cells that may have penetrated or could penetrate the prostate capsule. Side effects from surgery include incontinence and impotence. The cancer recurrence rate after surgery can be as high as approximately 35% at 5 years, and approximately 60% at 10 years, particularly when the prostatic-specific antigen level (discussed below) is greater than 10. Radiation therapy has short-term side effects such as skin reactions, fatigue and nausea. Additional long-term side effects of radiation therapy to the prostate include urinary incontinence (loss of bladder control) and impotence, as well as damage to surrounding organs.
Hormone therapy is also used to supplement prostate cancer treatments by stopping cancer cells from growing. Male hormones, such as testosterone, help cancer cells grow and, in contrast, female hormones or estrogens inhibit growth. Side effects of estrogen therapy include nausea and vomiting, hot flashes, fluid retention, weight gain, headaches and gynecomastia (an increase in breast tissue) in men.
Fundamentally, the problem with current prostate treatments is the inability to control microscopic capsule penetration from the prostate gland, which spreads the cancer to vital organs. Men with microscopic capsule penetration of cancer cells are not cured by radical prostatectomy. These microscopic cells may spread far from the prostate gland into vital organs by means of the lymphatic system or by blood vessels through the prostate capsule.
It is possible to detect the presence of prostate cancer by means of the well-known serum assay Prostate-Specific Antigen (PSA) test (M. K. Brawer, xe2x80x9cProstate-Specific Antigen: Current Status,xe2x80x9d CA A Cancer Journal for Clinicians, Vol. 49, pp. 264-281, 1999, and J. E. Oesterling, xe2x80x9cProstate Specific Antigen: A Critical Assessment of the Most Useful Tumor Marker for Adenocarcinoma of the Prostate,xe2x80x9d The Journal of Urology, Vol. 145, pp. 907-923, May 1991). The prostatic lumen contains the highest concentration of PSA in the human body. PSA is an enzyme produced in all types of prostatic tissue (normal, benign hyperplastic and malignant). In particular, PSA is a serine protease that is produced only by the epithelial cells lining the acini and ducts of the prostate gland; none of the other cellular components of the prostate, including the stromal and vascular elements produce PSA. Researchers have verified that PSA is produced in the epithelial cells of BPH tissue, primary prostate cancer tissue, and metastatic prostate cancer tissue. The serum PSA test detects a significant number of prostate cancers and the destruction of prostatic tumors leads to reduced PSA levels, since the body stops producing PSA when the tumors are eliminated. Currently, a PSA level of 4.0 ng/ml or greater is used to decide whether a patient will be biopsied to try to verify the presence of carcinoma in the prostate. Thus, patients with a PSA level under 4.0 ng/ml currently are not biopsied even if they experience the signs and symptoms of prostate cancer which may include: frequent urination, especially at night, inability to urinate, trouble starting or holding back urination, a weak or interrupted urine flow and frequent pain or stiffness in the lower back, hips or upper thighs.
In addition to PSA level, the Gleason Grade is used to histologically grade adenocarcinoma of the prostate (G. K. Zagars, et al, International Journal of Radiation Oncology Biology Physics, Vol. 31, No. 2, pp. 237-245, 1995), with Grade 1 being the least malignant and slowest growing. Gleason Grade 3 is the most commonly occurring grade when diagnosed. Gleason Grades 4, 5 and above (up to 10) are considered highly aggressive, rapidly growing carcinomas.
Biopsy results and staging are used to predict the behavior of the cancer and the likelihood of its spread. Stage 1 tumors are small and cannot be felt on rectal examination. Stage 2 or greater refers to prostates in which the tumor can be felt. Stage 3 cancers have spread beyond the boarders of the prostate. In Stage 4, which can be determined by imaging studies such as bone scans, CT, or MRI scans, the cancer has spread into nearby lymph glands, the bones, or elsewhere in the body. As is well known in the medical field, the earlier the cancer is detected, the better the chance of being a cancer survivor. If detection is not possible before stage 2, the next best medical option would be to safely treat apparently healthy tissue. Thus, there is a need to treat healthy tissue since cancer, in general, cannot be detected until it has reached stage 2 or a later stage.
There are four types of prostate ductal carcinomas: transitional cell carcinoma, intraductal adenocarcinoma, mixed ductal carcinoma, and endometrioid carcinoma. Transitional cell and mixed ductal carcinomas are aggressive cancers that require complete removal of the prostate and bladder if found while the tumor is still confined to the prostate. Complete removal of the prostate and bladder is also the medically accepted treatment for endometrioid carcinoma. Intraductal adenocarcinomas are treated by radical prostatectomy. Thus; there is a need for a system for treating and preventing the growth and spread of cancer that does not require surgical prostatectomy.
Benign Prostatic Hyperplasia
Benign Prostatic Hyperplasia (BPH) is described primarily as an enlargement of the prostate gland that exerts pressure on the urethra, resulting in obstruction of the flow of urine, and is a common affliction in middle-aged and older males. Approximately 50% of men older than 65 years will have BPH symptoms that significantly affect their quality of life. The American Urological Association (AUA) Symptom Index was developed to help categorize BPH symptoms. The AUA score has the following score ranges: 0 to 7 pointsxe2x80x94BPH symptoms are considered mild; 8 to 19 pointsxe2x80x94BPH symptoms are considered moderate; and 20 to 35 pointsxe2x80x94BPH symptoms are considered severe. However, many BPH patients do not seek treatment until their AUA score is about 12.
Over the last two decades, a number of treatments for BPH have been developed each with advantages and disadvantages. The major types of BPH treatment systems are: 1) transurethral resection of the prostate (TURP), 2) Transurethral Electrovaporization of the Prostate (TVP), 3) Drugs, 4) Interstitial Laser Coagulation, 5) RF Needle Ablation, and 6) Microwave Thermotherapy of the Prostate. Other treatment techniques have been explored, including transurethral incision of the prostate, prostatic stents, and balloon dilation, but are used to a lesser extent.
BPH treatment success and practicality can measured in terms of 1) efficacy, 2) durability, 3) level of pain (during and after the procedure), 4) recovery period, 5) complexity of the procedure, 6) cost of the procedure, and 7) side effects. Efficacy of BPH treatments is commonly quantified using the AUA Symptom Index (SI) and peak urine flow rate. Normal urine flow rate is about 16 ml/sec. Other optional tests such as residual urine volume and pressure flow are sometimes used to judge efficacy. Durability is the length of time for which the treatment is effective. The level of pain relates primarily to the need for either general anesthesia or local anesthesia. The recovery period is measured in terms of the number of days of hospitalization and home rest. The complexity of the procedure is a function of the length of the procedure, the training of the individual administering the procedure (either an urologist or a technician), the type of anesthesia required, and the length of time needed for Foley catheterization after treatment. The cost of the procedure is influenced strongly by the length and complexity of the procedurexe2x80x94particularly whether a hospital stay is required.
Until about 1990, the major treatment (xe2x80x9cGold Standardxe2x80x9d) for BPH was Transurethral Resection of the Prostate (TURP) which is administered by urologists. TURP is expensive, requires a long recovery time, and has a number of significant side effects, which has prompted the search for better treatment techniques. A summary of approaches to treat BPH, including surgery, drug and laser, RF, and microwave applications is described below.
Transurethral Resection of the Prostate (TURP):
The xe2x80x9cGold Standardxe2x80x9d of BPH treatments involves a surgical procedure in which a rigid transurethral scope with an electrosurgical loop is used to remove part of the enlarged prostate tissue (primarily the central zone of the prostate) with RF energy. In practice, 90% of surgical procedures for BPH involve TURP, due to its excellent efficacy (85% or more), long-term durability (10 to 15 years) for 90% of patients. On the order of 200,000 TURPs are performed in the United States annually. TURP has a number of drawbacks: It is a very painful procedure and requires both 2-4 days of hospitalization and 2-4 weeks of recovery at home. The TURP procedure is performed in about one hour and requires general anesthesia. An urologist must perform the procedure. A Foley catheter is required for about 2-3 days post treatment. Some of the major potential side effects of a TURP include impotence, incontinence, high blood loss, and retrograde ejaculation.
Open Prostatectomy:
An open prostatectomy is primarily used on patients with very large prostates with excellent results: the efficacy is greater than 95% and the durability is the same as TURP (10 to 15 years). With any surgical procedure, the pain level is very high and general anesthesia is required. About 7 to 10 days of hospitalization is required with an additional 3-5 weeks spent at home. The procedure takes a few hours and must be performed by a urologist. Following the treatment, a Foley catheter must be used for 2-4 days to drain the bladder. An open prostatectomy is about twice the cost of a TURP, and has the serious potential side effects and complications including high blood loss, impotence, and incontinence.
Transurethral Electrovaporization of the Prostate (TVP):
Basically a modification of TURP, transurethral electrovaporization of the prostate employs a grooved electrosurgical rollerball electrode to channel open the urethra that is blocked by the prostate tissue. The TVP procedure is safer and has minimal side effects compared to TURP. The efficacy is excellent (85%), but still is a very painful procedure requiring 2-4 days of hospitalization and 1-2 weeks at home. A urologist performs this 60-minute procedure and the patient is under a general anesthetic. A Foley catheter must be used for 2-4 days following this procedure. The procedure costs slightly less than TURP. There is less blood loss than with TURP, but their are still the potential side effects of impotence, incontinence, and retrograde ejaculation.
Transurethral Incision of the Prostate (TUIP):
In a relatively new procedure for patients with small prostates, transurethral incision of the prostate provides an efficacy of about 80%. However, TUIP is not effective on large prostates. A minimal amount of prostate tissue is removed in this procedurexe2x80x94a simple incision is made along the entire length of the prostate. The TUIP procedure allows the bladder neck to spring open, allowing free urinary flow. The durability is expected to be similar to TURP, but clinical research is still in progress. This procedure is moderately painful and requires only a day or two of hospitalization, or for some patients is an outpatient procedure. Usually, 4 to 7 days of home rest are needed following the procedure. A urologist must perform this 60-minute surgical procedure and a Foley catheter must be used for 2 to 4 days. The cost of the TUIP is about the same as TURP. There is less blood loss with this procedure compared to TURP, but there are still the potential side effects of impotence, incontinence, and retrograde ejaculation.
Balloon Dilation:
For patients with small prostates, balloon dilation within the prostatic urethra can be used to offer some relief from BPH symptoms. The efficacy is only about 60% and the durability is only 1 to 5 years. This procedure is less costly than TURP and is usually performed as an outpatient with several days of home rest. The procedure is performed under local anesthesia by a urologist in about 30 minutes. A Foley catheter is required for about 2-4 days. There may be some bleeding in this procedure and there are the possible side effects of infection and impotence. The procedure does not work well on large prostates.
Stents:
For very ill patients with small prostates, stents can be used with good effectiveness to improve BPH symptoms. Durability is not a major issue since these patients are usually very ill with other diseases. This procedure is moderately painful and requires only local anesthesia, is performed in about 30-minutes by a urologist, and is done as an outpatient with about 4-5 days of home rest. The cost of this procedure is less costly than TURP. Some of the potential side effects are irritation, infection, and the formation of debris on the stent.
Drugs:
Two categories of drugs are used in treating BPH. One category uses an alpha blocker (Hytrin or Cardura) to relax the muscles that surround the prostate to allow better urinary flow. The other type of drug is reductase inhibitor (Proscar) which actually shrinks the prostate gland. Hytrin, for example, has very good efficacy (74%) and offers some immediate relief of BPH symptoms, however 2-3 weeks are needed until the full effectiveness is reached. Clinical data suggests that this drug has at least 3 to 5 years durability and is simply prescribed by a general practitioner. The cost is less than TURP depending on the number of years of treatment. There can be some serious side effects such as dizziness, chest pain, irregular heartbeat, and shortness of breath.
Proscar works well on large prostates, but is ineffective on small prostates. Full effectiveness of the drug takes about 3 to 6 months and the durability is estimated at least 3 to 5 years. This drug is prescribed by a general practitioner and must be taken for at least 12 months. The cost of the drug is less than TURP. Some of the known side effects are impotence, swollen lips, decreased volume of ejaculate, and skin rash.
Interstitial Laser Coagulation:
Here, an interstitial laser coagulation surgical device delivers laser energy radially along the length of a custom-designed light diffuser. The diffuser produces an ellipsoidal pattern of thermal damage, applying the laser energy omnidirectionally and uniformly, to maximize treated tissue volume in the prostate. This is a moderately painful surgical procedure, requiring one or two days in the hospital and then 1 to 2 weeks at home. This 30-minute procedure must be performed by a urologist, with a choice of either general or local anesthesia depending on the patient""s condition. A serious disadvantage with this procedure is the lengthy required time of 1 to 2 weeks in which a Foley catheter must be used to drain the bladder of urine. The cost of the procedure is less than TURP. There are many potential side effects from this treatment including impotence, incontinence, blood loss, and retrograde ejaculation.
RF Needle Ablation (Transurethral Needle Ablation):
This system uses two high-energy RF (approximately 0.47 MHz) needles that are inserted through the urethra into the prostate, to ablate the prostate tissue in a few minutes. More than 10,000 patients worldwide have been treated with this system, which provides good to very good efficacy. There is only limited 12-month durability data for this system, so the long-term effectiveness is not known. The procedure is moderately painful (local anesthesia required) and is performed as an outpatient with 1-2 weeks for home recovery. The procedure is usually performed by a urologist in about 30 minutes. About 40% of patients will require a Foley catheter for about 2 to 3 days. The procedure costs less than TURP. The major side effects from this procedure are irritating voiding, erectile dysfunction, and retrograde ejaculation.
In view of the known treatments for BPH, which require costly, painful surgery or drugs which have potentially dangerous side effects, there is a need for a system of treating benign prostatic hyperplasia (BPH) that is not painful; can be accomplished on an outpatient basis; and quickly restores the patient to his normal functions. In addition, a method is needed that can safely treat the prostate gland with focussed energy before a significant amount of microscopic tumor cells form in the prostate.
The above problems associated with known treatments are solved by the system and method for using the system according to the invention. The system and method according to the invention safely heat pre-cancerous, cancerous, pre-benign, and benign conditions of the prostate by heating the prostate gland with focussed or concentrated energy, such as microwave energy, delivered by either phase non-coherent or coherent array applicators in the urethra and rectum, or with interstitial applicators positioned within the prostate. In a non-coherent array, separate microwave oscillators can drive the applicators and there is no common phase relation. In a phase coherent array (phased array), a single microwave oscillator can drive multiple applicators with a common phase relation.
The Applicants"" approach is to treat the prostate gland with focussed energy, such as microwave energy before a significant amount of microscopic tumor cells form in the prostate gland. As described above, all past uses of thermal therapy were used for the treatment of established prostate cancers with moderate to high PSA levels (over 4.0 ng/ml) or for the treatment of moderate to severe AUA symptom index scores for BPH. The preferred embodiment of this invention is for the prevention or before detection, or before medical intervention is required. Thus, the inventive method is for treating prostate cancer when the PSA level is less than 4.0 ng/ml, or for treating BPH where BPH symptoms are less than severe or the AUA symptom index score is less than 13. In other words, the inventive method is to prevent the cancer or BPH from developing into a significant problem for a patient (i.e., before serious adverse effects occur).
The preferred method of treating a prostate, according to the invention, is with a coherent adaptive phased array and comprises the steps of monitoring temperatures of walls of the urethra and rectum, orienting two microwave applicators in at least one of the urethra and rectum, adjusting the microwave power to be delivered to the prostate based on the monitored urethral and rectal wall temperatures, monitoring the microwave energy dose delivered to the prostate being treated and automatically completing the treatment when a desired total microwave energy dose has been delivered by the microwave applicators.
Incoherent-array or non-adaptive phased array hyperthermia treatment systems can be used to heat semi-deep and deep tissue, depending on the radiating frequency. Due to the dielectric heating of high-water content tissue such as prostate tumor, it may be possible to safely heat prostate tumors with either non-coherent arrays or non-adaptive phased arrays.
Moreover, the system and method according to the invention have application in situations where there is no well-defined position to place the temperature feedback sensor, or where it is desirable to avoid inserting a temperature probe into the prostate tissue. In the case of a single applicator, an E-field probe (or E-field sensors) is not necessary and thus, an invasive probe is not required in the preferred system and method according to the invention. The inventive system and method may destroy all of the prostate pre-cancerous and cancerous cells or benign lesions with heat generated by the focussed energy thereby avoiding further progression of the cancer cells or benign lesions.
In addition, the method according to the invention can be used to enhance radiation therapy or for targeted drug delivery and/or targeted gene therapy delivery with or without thermosensitive liposomes as described in U.S. Pat. No. 5,810,888 to Fenn.
The method according to the invention destroys the pre-cancerous, cancerous, pre-benign, and benign cells in the prostate while preserving normal prostate tissue. Thus, the system and method according to the invention achieves a thermal prostatectomy and avoids damage to healthy tissue. Accordingly, the inventive method is a prostate conservation technique.
The urethral and rectal wall temperature can be measured by temperature probe sensors positioned away from the transurethral and transrectal applicators to obtain the true temperature of the urethral and rectal walls. Alternatively, the tissue temperatures can be monitored by external means, including infrared, laser, ultrasound, electrical impedance tomography, magnetic resonance imaging, and radiometry techniques as known in the art.
Alternatively, a temperature probe could be inserted at an appropriate depth in the prostate tissue to monitor the temperature thereof. As discussed below, insertion of a temperature probe is not a preferred embodiment.
In an embodiment with two or more energy applicators, an invasive E-field probe, inserted in the prostate, may or may not be used to measure the microwave power delivered to the tissue to be treated to determine the length of the focussed energy treatment. In a preferred embodiment, the invasive E-field probe can be used to focus the applied energy at the E-field probe inserted in the prostate.
As an alternate embodiment, for a coherent phased array, two E-field sensors can be placed in the prostatic urethra and rectum non-invasively and be used to null the E-field in the urethra and rectum and effectively focus the microwave radiation in the prostate tissue. Additionally, the microwave phase for the transurethral and transrectal applicators can be adjusted so that the microwave energy is scanned across an area of the prostate.
The system and method according to the invention can be achieved with or without compression of the prostate. In a preferred method, a patient""s prostate would be compressed by expanding at least one of a urethral balloon and a rectal balloon. Focussed energy and prostate compression provide preferential heating of high-water content prostate carcinoma and benign cells in the prostate compared to the surrounding lower-water content normal prostate tissues and tissue surrounding the prostate.
To coherently focus the energy, such as microwave energy, in the prostate, the patient""s prostate can be compressed via a urethral and rectal balloon and means for determining where to focus the energy in the patient""s prostate is used. The means for determining where to focus the energy can be either a single electric-field probe, inserted in the central portion of the prostate, or two noninvasive electric-field sensors on the urethral and rectal walls. The probe or sensors receive signals that can be used to measure a feedback signal in order to adjust the energy phase delivered to the applicators located in the urethra and in the rectum.
The major advantages offered by treatment according to the system and method of the invention over known treatments are listed below:
1. Prevention and destruction of prostate tumors (including cancerous and benign);
2. Immediate relief from any BPH symptoms that might exist;
3. Long term durability;
4. Only low level pain may be experienced;
5. Outpatient procedure;
6. Local anesthesia;
7. No Foley catheter required; and
8. No significant side effects or complications.
A biological stent can be formed in the prostatic urethra due to the combination of compression balloon dilation and microwave heat (microwave urethroplasty) as evidenced in clinical tests held by the assignee, Celsion Corporation, during 1999. As a result, one of the major deficiencies in known BPH treatments, namely the need for a Foley catheter for several days, is no longer needed and a patient may experience immediate relief from BPH symptoms.
As described below, applicants"" inventive system and method involves monitoring the microwave energy dose delivered to the prostate being treated and completing the treatment based on the total microwave energy dose that has been received. That is, conventional temperature feedback measurements of tumor thermal dose can be replaced with the total microwave energy delivered to the coherent phased array or non-coherent microwave applicators and then to the treated area. Accordingly, with the instant invention, instead of temperature feedback measurements, which require the insertion of a temperature feedback probe into the prostate and its inherent problems, microwave energy dose is used as a feedback to determine the required length of treatment. In this application the term xe2x80x9cmicrowave energy dosexe2x80x9d (in Joules or watt-seconds) is similar to the dose used in radiation therapy, namely the radiation absorbed dose (Rad) which is a unit of absorbed dose of radiation defined as deposition of 100 ergs of energy per gram of tissue.
Thus, the instant method for selectively heating cancerous and benign conditions of the prostate avoids the risk of spreading cancer cells since the temperature probe is not inserted into the treated area (tumor bed) of the prostate. The elimination of an inserted temperature probe reduces the risk of infection to a patient as a result of the inserted probe. Likewise, the microwave field applied to a tumor would not be subjected to scattering or other disturbance caused by a temperature probe, especially a metallic probe. In addition, the time and costs associated with inserting the temperature probe are saved.
The inventive system and method may also be used to treat healthy prostate tissue or undetected high-water content microscopic pre-cancerous or pre-benign cells in seemingly healthy prostate tissue to prevent the occurrence of or recurrence of cancerous conditions of the prostate. Thus, the system and method according to the invention would be able to destroy or ablate microscopic precancerous or pre-benign cells in the prostate gland that are higher in water content (e.g., 90%) than the prostate gland (e.g., 80%) before they are detected. This would be an early treatment that could prevent cancer from growing in the prostate and spreading from the prostate, or enlargement of the prostate gland. In the case of seemingly healthy tissue, the prostate tissue would be irradiated with microwave energy focused at high-water content microscopic cells that are known to form lesions without damaging the healthy lower-water content prostate tissue.
If both transurethral and transrectal applicators are used and both are expanded by respective balloons, a preferred system having means for compressing and immobilizing the prostate to reduce the tissue penetration depth and to reduce the prostate blood flow is achieved.
In an alternate method, the prostate is compressed with a single transurethral balloon, which immobilizes the prostate tissue, reduces blood flow, and reduces the penetration depth required for the microwave radiation. The compression balloon is made of a microwave transparent plastic material such as Latex. The placement of an E-field feedback probe in the prostate may be achieved with an ultrasound transducer or other type of image guidance. Further reduction in blood flow can be achieved, in a preferred method, by injecting a local anaesthetic lidocaine with ephinephrine or anti-angiogenesis drug in the prostate.
Two microwave applicators (such as described by U.S. Pat. No. 5,007,437 to Sterzer which is incorporated herein by reference) can be positioned transurethrally and transrectally. A phased array can be achieved with a multiple number of applicators greater than or equal to two. In a preferred embodiment, coherent 915 MHz microwave power is delivered to the two transurethral and transrectal applicators, at a predetermined power level, while phase shifters in each channel are adjusted to maximize and focus the microwave energy at the E-field probe sensor. Water-cooling within the catheters and balloons allows cooling of the urethral and rectal walls. Additional interstitial applicators can be inserted within the prostate to supplement the heating that is produced by the transurethral and transrectal applicators.
During the hyperthermia treatment, the microwave power level delivered to each of the applicators may be adjusted either manually or automatically to avoid high temperatures that could cause burns or blisters to the urethral or rectal walls. In addition, the amount of prostate compression, if used, is adjusted as necessary during treatment to provide patient comfort. Each time the prostate compression is adjusted, the microwave-energy/phased array is refocused so that the E-field probe sensor receives maximum power. The total microwave energy, since the start of the treatment, delivered to the microwave applicators is monitored during the treatment. The treatment is completed when a desired amount of total microwave energy is delivered to the microwave applicators, which indicates that the lesion cells are significantly (i.e., thermal downsizing) or completely destroyed (i.e., thermal prostatectomy).
In order to determine the effectiveness of the treatment, the prostate tissue may be imaged and examined with one of x-ray, ultrasound, and magnetic resonance imaging before and after the microwave total energy dose is administered, as well as with pathological results from needle biopsy of the prostate tissues.
In an alternate embodiment of the invention, the single invasive E-field probe is replaced with two E-field sensors positioned in the urethra and rectum and the coherent array is phase focused by minimizing (nulling) the individual or combined power received by the two sensors, providing a completely noninvasive treatment. In a preferred embodiment, the two E-field sensors are contained with catheters attached to the outside surface of a compression balloon which provides a pressure contact to the urethal and rectal walls. Algorithms are used in conjunction with the feedback signals sensed by the E-field sensors to null areas on the urethal and rectal walls outside thereby focussing the applied energy on an internal site. After ther nulling algorithm is completed, the E-field sensors can be withdrawn and temperature sensors can be inserted to measure the urethal and rectal wall temperatures.
Such a totally non-invasive hyperthermia treatment where E-field sensors and temperature sensors monitor the urethral and rectal walls would provide an effective method of destroying benign and cancerous lesions in the prostate. In an embodiment with non-coherent applicators, an E-field focussing probe and phase shifters are not required to heat the tissue. With non-coherent energy, only the applicator radiated power is additive and phase shift is not used.
While the preferred embodiment is described with reference to adaptive microwave phased array technology, Applicants"" system and method may be achieved by focussing energy, in general, to heat and ablate an area of tissue. The focused energy may include electromagnetic waves, ultrasound waves or waves at radio frequency. That is, applicants"" inventive system and method includes any energy that can be focused to heat and ablate an area of tissue. This energy, such as microwave or ultrasound energy, can be coherent or non-coherent.
In yet another embodiment of the invention with a coherent phased array, the boundary of an area of tissue to be treated in a body (e.g., prostate) is calculated, an E-field probe may be inserted in the body or at least two E-field sensors are positioned within the urethra and rectum; and energy is applied through applicators to the area to be treated. In this embodiment, the focus of the energy would change so that the focus scans the area to be treated. That is, there is no longer a fixed focus spot as the relative phase of the applied energy would be adjusted so that the focus moves inside the area to be treated thereby obtaining a geometric shape of heating.
A fixed focus spot is determined through the appropriate algorithm. Then, for example, the relative phase of the applicators to obtain this fixed focus spot is adjusted 30xc2x0 one way and then 30xc2x0 the other way to xe2x80x9cscanxe2x80x9d a larger heated/treated area. Depending on the size of the area to be treated the scan may focus between 180xc2x0 and 90xc2x0 or 60xc2x0 or 120xc2x0.